I assume you are talking about the Area Manager, not categories. If I click "Add Area", I can only get the page to refresh when I click Save by entering an error, like a value for Title that was already used by another area/wiki page. However, when I do this, most of the options I selected before still show the choices I made (nothing was reset). The only thing that is unchecked is the Parsing Options, which have numbers instead of the descriptions.
When the page refreshes, at the top you will probably see a section called "Errors" and "The following problems were found with your submission:"
What errors does it tell you?